In a Long Term Evolution (Long Term Evolution, LTE) system and its subsequent evolution, a quantity of antennas at a data transmit end increases rapidly, and a quantity of user equipments (UEs) that need to be served also increases rapidly. An increase in the quantity of antennas can provide a higher spatial degree of freedom, thereby creating an advantageous condition for multiplexing multiple data streams in downlink space (for example, single user multiple-input multiple-output (SU-MIMO) or multi-user multiple-input multiple-output (MU-MIMO)). Downlink channel state information (CSI) measurement is classified into two types: obtaining instantaneous CSI, for example, a channel; and obtaining statistical CSI, for example, a channel autocorrelation matrix. A function of a massive MIMO system lies more in statistically performing channel processing, including dimension reduction and grid of beam (GOB).